| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Received August 9, 2007
Revised September 13, 2007
Accepted after revision September 25, 2007
1 Manchester Metropolitan University
2 University of Nottingham
3 University
4 Keele University School of Medicine
5 Karolinska Institute
6 University of Nottingham Schoolof Graduate Entry Medicine and Health
* To whom correspondence should be addressed. E-mail: michael.rennie{at}nottingham.ac.uk.
We hypothesized that rates of myofibrillar and patellar tendon collagen synthesis would fall over time with disuse, the changes being accompanied in muscle by decreases in focal adhesion kinase (FAK) phosphorylation and in gene expression for proteolytic enzymes. We studied nine men (22± 4 y, BMI 24±3 kg.m-2 (means ± SD) who underwent unilateral lower leg suspension for 23 d; five were studied between 0 and 10 and four between 10 and 21 days. Muscle and tendon biopsies were taken in the post-absorptive state at days 0, 10 and 21 for measurement of protein synthesis, gene expression, and protein phosphorylation. Muscle cross sectional area decreased by 5.2% at 14 d and 10.0% (both P<0.001), at 23 d, i.e. 0.5 %.d-1, whereas tendon dimensions were constant. Rates of myofibrillar protein synthesis fell (P<0.01) from 0.047%.h-1 at day 0 to 0.022 %.h-1 at 10 d without further changes. Tendon collagen synthetic rates also fell (P<0.01) from 0.052 to 0.023 %.h-1 at 10 d and then to 0.010%.h-1 at 21 d. FAK phosphorylation decreased 30 % (P<0.01) at 10 d. No changes occurred in the amounts/phosphorylation of PKB-P70s6K-mTOR pathway components. Expression of mRNA for MuRF-1 increased ~3-fold at 10 d without changes in MAFbx or tripeptidyl peptidase II mRNA, but all decreased between 10 and 21 d. Thus, both myofibrillar and tendon protein synthetic rates show progressive decreases during 21 d of disuse; in muscle, this is accompanied by decreased phosphorylation of FAK, with no marked increases in genes for proteolytic enzymes.
This article has been cited by other articles:
|
|
 |
|
  P. A. Tesch, F. von Walden, T. Gustafsson, R. M. Linnehan, and T. A. Trappe Skeletal muscle proteolysis in response to short-term unloading in humans J Appl Physiol, September 1, 2008; 105(3): 902 - 906. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. Christensen, E. Dyrberg, P. Aagaard, S. Enehjelm, M. Krogsgaard, M. Kjaer, and H. Langberg Effects of long-term immobilization and recovery on human triceps surae and collagen turnover in the Achilles tendon in patients with healing ankle fracture J Appl Physiol, August 1, 2008; 105(2): 420 - 426. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Rennie Mysterious properties of tendon metabolism J Appl Physiol, August 1, 2008; 105(2): 397 - 397. [Full Text] [PDF]
|
|
|
|
 |
|
 E. I. Glover, B. R. Oates, J. E. Tang, D. R. Moore, M. A. Tarnopolsky, and S. M. Phillips Resistance exercise decreases eIF2B{varepsilon} phosphorylation and potentiates the feeding-induced stimulation of p70S6K1 and rpS6 in young men Am J Physiol Regulatory Integrative Comp Physiol, August 1, 2008; 295(2): R604 - R610. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
